Backbone networks, which may also be called core networks, include networks designed to provide a path for the exchange of information between different local area networks (LANs) or subnetworks. A core network can tie together diverse networks in the same building, in different buildings in a campus environment, or over wide areas. Typically, a core network is a higher bandwidth network than the LANs or subnets that it connects.
As an example of a core network, a large corporation that has many locations may have a core network that ties all of the locations together. As another example, a service provider may maintain a core network that may be leased by customers.
Core networks may be particularly used as a provider bridge network (PBN). In such an implementation, two or more LANs or subnetworks may be connected over a core network in which the core network acts as a bridge. One standard for implementing provider bridge networks is the IEEE standard 802.1ah.
In a PBN, it may be desirable to provide redundant connections from a LAN/subnetwork to the PBN. For example, a customer edge (CE) device in the access network (i.e., the LAN or subnetwork that connects to the core network) may connect to two or more provide edge (PE) devices in the core network.
Other types of core networks include a provider backbone bridge network (PBBN) and a virtual private LAN service (VPLS). With these networks, as with a PBN, it may be similarly desirable to provide redundant connections from the LAN/subnetwork to the PBBN or VPLS core network.